Systems and methods for distributing content in a vehicle-based wireless network

ABSTRACT

Techniques for distributing content to mobile computing devices, such as in the context of a vehicle-based wireless network, are described. In some examples, a content provider uses a cellular network to initially transmit a content item to a multi-network communication device in a first vehicle. The first vehicle device then uses a local Wi-Fi network to further transmit randomly selected portions of the content item to devices on nearby vehicles, which may also further propagate the content item portions to other vehicles. Vehicle devices may also specifically request content portions by broadcasting requests to neighboring vehicle devices via local Wi-Fi communication and/or communicating with the content provider via the cellular network. Upon the occurrence of a condition, such as a passage of time, the content provider may also initiate communication with devices in the network in order to assure complete distribution of the content item.

PRIORITY CLAIM

This application claims the benefit of U.S. Provisional PatentApplication No. 62/361,368, entitled “SYSTEMS AND METHODS FORDISTRIBUTING CONTENT IN A VEHICLE-BASED WIRELESS NETWORK” and filed onJul. 12, 2016, the content of which is incorporated herein by referencein its entirety.

TECHNICAL FIELD

The present disclosure relates to methods, techniques, and systems fordistributing content to mobile computing devices and, more particularly,to methods, techniques, and systems for efficiently distributing contentover a vehicle-based wireless network.

BACKGROUND

Content providers, such as vehicle manufacturers, fleetoperators/managers, media providers and other entities andorganizations, have a need to distribute content items to vehicles. Forexample, a vehicle manufacturer may desire to update software for one ormore subsystems (e.g., engine control, media center, navigation system)in a particular model of car. Historically, such an update was onlypossible via a manual update performed by a technician in a servicecenter.

Vehicles increasingly include wireless communication devices that enablecommunication via the cellular phone network, Wi-Fi, Bluetooth, or thelike. These additional communication mechanisms allow content providersto distribute content items “over the air,” while vehicles are in thefield, without requiring the physical presence or manual intervention ofa technician, operator, owner or other party.

FIGS. 1A and 1B illustrate a prior art approach to the over the airdistribution of content items to vehicles using a cellular wirelessnetwork. In FIG. 1A, a carrier 110 operates a cellular network, which isused by a content provider 112 transmit content item A to each ofmultiple cars 101 a-101 e. To transmit the content item to, for example,car 101 a, the content provider 112 connects (via the carrier 110) to acellular communication device (not shown) the car 101 a, and thentransmits the content item via the established connection. This processis repeated for each and every car 101 a-101 e. In this example, thecontent provider 112 transmits content item A five times in all, once toeach car 101 a-101 e.

FIG. 1B is a sequence diagram that illustrates the prior art contentdistribution process. In FIG. 1B, the carrier 110 communicates with eachof multiple communication devices 102 a-102 c. The communication devices102 a-102 c may be cellular communication devices that are eachinstalled in a corresponding vehicle. The carrier transmits the entirecontent item to each of the devices 102 a-102 c via a dedicatedconnection. As carrier charges are typically based on the amount of datatransmitted, the distribution cost of one content item is proportionalto the number of destination devices (vehicles).

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate a prior art approach to the distribution ofcontent items to vehicles using a cellular wireless network.

FIGS. 2A and 2B illustrate the distribution of content items to vehiclesaccording to an example embodiment.

FIG. 3 is a sequence diagram that illustrates a content itemdistribution process according to an example embodiment.

FIGS. 4A-4D illustrate automatic rate control according to an exampleembodiment.

FIG. 5 is a sequence diagram that illustrates an automatic rate controlprocess according to an example embodiment.

FIGS. 6A-6M are example flow diagrams of content distribution processesperformed by example embodiments.

FIG. 7 is a block diagram of an example computing system or device forimplementing and performing content distribution according to an exampleembodiment.

DETAILED DESCRIPTION

Embodiments described herein provide enhanced computer- andnetwork-based methods, devices, and systems for efficiently distributingcontent to mobile computing devices and, more particularly, to methods,techniques, and systems for efficiently distributing content over avehicle-based wireless network.

In the following, Section 1 provides an overview of a contentdistribution architecture. Section 2 describes a content distributionprocess implemented by some embodiments. Section 3 describes automaticrate control techniques, in which communicating devices independentlyvary their transmission rates in order to optimize or at least improvethroughput, network connectivity, and/or range.

1. Overview

FIGS. 2A and 2B illustrate the distribution of content items to vehiclesaccording to an example embodiment. In contrast to the prior artapproach described with respect to FIG. 1A, the content item istransmitted in FIG. 2A by the carrier 110 to a subset of the cars 101a-101 e, from whence it is then further distributed to other cars via asecond network, such as via one or more Wi-Fi network establishedamongst the cars 101 a-101 e.

In the example of FIG. 2A, the content provider 112 uses the cellularnetwork managed by the carrier 110 to initially transmit content item Ato car 101 a. Content item A is decomposed into portions (also referredto as “segments”). In this example, content item A is decomposed intothree portions, A1, A2, and A3. Segmenting the content item allows forimproved restart behavior in the face of dropped transmissions, becausethe entire content item need not be retransmitted. In addition,segmenting the content item allows for multiple distinct entities tooperate as sources for various portions of the content item, therebyenabling a peer-to-peer distribution technique described herein.

Once car 101 a has received one or more of the portions A1-A3, the car101 a can begin distributing the received portions to other cars. Inthis example, car 101 a transmits, via one or more Wi-Fi networks,portions A2 and A3 to car 101 b; portions A1 and A2 to car 101 c;portions A1 and A3 to car 101 d; and portions A1 to car 101 e.

The portions transmitted by from one car to another may be selected invarious ways. In a preferred embodiment, the portions are selected atrandom. For example, car 101 a may randomly select portion A1 and thenbroadcast that portion via a Wi-Fi transceiver. Any other cars that arewithin the range of the Wi-Fi transmission from car 101 a will receivethe portion A1. Having transmitted portion A1, car 101 a selects anotherportion for transmission, and so on. In some embodiments, a transmittedportion will not be retransmitted until all of the other portions havebeen transmitted at least once. Once car 101 a has transmitted all ofportions A1-A3 at least once, it may once again begin to randomlydistribute that set of portions. In other embodiments, car 101 acontinuously transmits the portions A1-A3 in sequence instead of viarandom selection.

As the other cars 101 b-101 e receive portions of the content item, theytoo begin distributing the received portions to other cars. For example,car 101 c, having received portion A1 from car 101 a, transmits thatportion to car 101 b. Also, car 101 e and car 101 d exchange portions A2and A3.

Note that the content provider 112 may use the cellular network of thecarrier 110 to transmit portions to cars other than car 101 a. In somecases, one or more portions of content item A may be “pushed” to othercars, in order to seed more cars with portions of the content item.Alternatively, the portions may be transmitted in an on-demand manner.For example, car 101 c, understanding that it has not yet receivedcontent portion A3 from a neighboring car, may request and obtaincontent portion A3 from the content provider 112 via the cellularnetwork.

Note that in some embodiments, the content provider 112 will interact(via carrier 110) with each of cars 101 a-101 e in order to guaranteethat each and every car has received the content item. For example, thecontent provider 112 may initially transmit the entire content item tosome subset of the cars 101 a-101 e. Then the content provider 112 willwait in order to allow the initial subset of cars to share their contentvia their Wi-Fi transceivers. The wait time may be predetermined (e.g.,4, 8, 24 or 48 hours) or based on conditions (e.g., when the average carhas received at least N% of the content).

For example, the content provider 112 can periodically sample a subsetof the cars in order to estimate how much of the content item has beendistributed. When more than a specified fraction of the content item hasbeen distributed, the content provider 112 can then in a furtherinteraction (via the carrier) to transmit remaining content portions tothose cars that require them. In another approach, the content provider112 monitors the rate of change of the distribution of the content item.For example, the content provider can monitor (via sampling) the numberof bytes received per unit time by an average car. Then, when the ratedrops below some threshold, begins to plateau, or matches some othercondition, the content provider 112 engages in further interaction (viathe carrier) to transmit any remaining content portions.

Note that by employing such conditional distribution, the contentprovider 112 can trade off carrier costs for time in a reasonableprecise manner. For example, by waiting until cars have received (viasharing) 50% of the content item, the carrier can expect to save about50% in carrier costs.

FIG. 2B is a sequence diagram that illustrates the content distributionprocess of FIG. 2A. In FIG. 2B, the carrier 110 communicates with eachof multiple communication devices 100 a-100 c. In the context of FIG.2A, the communication devices 100 a-100 c may be multi-networkcommunication devices that are each installed in a correspondingvehicle. In other contexts, the communication devices may be personalmobile devices (e.g., smart phones) that are carried by human users. Amulti-network communication device 100 is described in greater detailwith respect to FIG. 7, below.

In the scenario of FIG. 2B, the carrier 110 transmits the entire contentitem to device 100 a. Device 100 a then transmits at least some of thecontent item to device 100 b. As noted above, the content shared bydevice 100 a may be selected at random, or by some other mechanism.Device 100 b obtains the remainder of the content item from the carrier110, such as by transmitting a request for one or more missing portionsto the carrier 110. In addition, device 100 b transmits the content itemto device 100 c, such as by transmitting the portions received fromdevice 100 a and directly from the carrier 110.

Note that in the examples of FIGS. 2A and 2B, the content provider doesnot transmit any portions of the content items to one or more remotedevices. For example, in FIG. 2A, cars 101 d and cars 101 b obtain theentire content item (portions A1-A3) from other cars, without needing tointeract with (and correspondingly utilize the cellular network) thecontent provider at all. Also, in FIG. 2B, device 100 c obtains thecontent item entirely from device 100 b, and does not interact with thecarrier 110 in any way.

Multi-network communication devices may also be fixed in location. Forexample, in a transportation related context, such devices may belocated near roadways to facilitate the distribution of content and/orother data (e.g., traffic flow data, warnings, road conditions data) tovehicles in the network. In a personal mobile device context, some fixedposition devices may also be employed to facilitate the distribution ofcontent. For example, devices may be located throughout a workplace,university campus, factory, or other facility, such that they cantransmit and receive data to and from personal mobile devices.Fixed-location devices may have all or some of the characteristics ofthe described mobile devices, as discussed herein. Specifically, theymay be multi-network devices that behave in a manner similar to mobiledevices, in that they may receive content from the content distributor(via a cellular network) and forward that content to other devices (viaa Wi-Fi network). They may also transmit (via Wi-Fi) content portionsreceived (via Wi-Fi) from passing vehicles to other vehicles.

2. Content Distribution

FIG. 3 is a sequence diagram that illustrates a content itemdistribution process according to an example embodiment. Moreparticularly, FIG. 3 shows interactions between a carrier 110 and twomulti-network communication devices 100 a and 100 b.

First, the carrier 110 transmits an announcement to device 100 a. Theannouncement is typically a message that identifies the content itemthat is being distributed by the carrier 110. The message is typicallysigned by the carrier 110 and/or the content provider 112, so thatdevice 100 a can evaluate the authenticity and source of the message.

Once device 100 a receives the announcement, it determines that it hasnot yet received the identified content item or any portions thereof. Inresponse, the device 100 a transmits to the carrier 110 a request forthe entire content item. In response, the carrier 110 transmits to thedevice 100 a a set of proofs and the content item. The proofs securelyidentify the portions that form the content item being distributed. Theproofs allow the device 100 a (or some other device) to verify theauthenticity and/or content of each of the portions, such as byincluding cryptographic hashes of each of the content items. In oneembodiment, the proofs are based on a hash tree, also known as a Merkletree. The leaves of the tree are hashes of each of the content portions,while each internal node of the tree is a hash of the concatenation ofthe hashes of the child nodes. The root node hash is typically digitallysigned by the carrier or content distributor, so that the root hash canbe verified as authentic. Given an authentic root node, other nodes neednot be obtained from a trusted source or otherwise signed, because theirintegrity and authenticity can be ultimately verified with respect tothe root hash. The advantage of using a hash tree is that a device 100 acan authenticate and/or verify the integrity of any received contentportion without having received the entire tree, thereby enabling randomdistribution of content portions. For example, to authenticate a singlecontent portion, a device need only have possession of the contentportion and the branch of the tree between the tree root and the contentportion.

Next, the carrier 110 begins to transmit to the device 100 a the contentitem, typically by transmitting the content portions in sequence. Oncethe device 100 a has received at least some of the content portions,device 100 a begins to randomly broadcast portions to neighboringdevices.

In this example, device 100 b receives a first portion. Each portionidentifies its corresponding content item (e.g., a unique filename ofthe content item). Having never received the identified content item,device 100 b requests the corresponding announcement and proofs fromdevice 100 a. In response, device 100 a forwards the announcement andproofs to device 100 b.

Device 100 a executes a distribution loop in which it shares the contentitem with its neighbors. The content item is shared by randomlyselecting and broadcasting content portions and/or responding torequests for specific content portions. Different types of requests arecontemplated. For example, device 100 b may transmit (e.g., broadcast) arequest that includes a content identifier and one or more portionidentifiers (e.g., a segment list). Such a request may be transmitted,for example, if device 100 b seeks one or more content portions in orderto complete a particular content item.

The operation and termination of the distribution loop performed bydevice 100 a may be governed by various factors. For example, the loopmay operate for a length of time, such as may be specified by theannouncement for the content item. Alternatively, the loop may operateuntil demand (e.g., as measured based on the number of requests forcontent portions) falls below a specified level (e.g., less than onerequest per minute. In another embodiment, the loop may operate untilpeer vehicles have received at least a specified average fraction orshare of the total number of content portions (e.g., until each devicehas received at least 90% of the portions). The number of portionsreceived by devices may be determined by incorporating in a request fora specific portion the number of received (or missing) portions. In someembodiments, the distribution loop performs random distribution untilsome stopping condition is reached (e.g., neighboring devices havereceived at least 90% of the portions), and then continues thedistribution loop only in an on-demand mode, in which requests forspecific portions are serviced but no random distribution takes place.After termination of the distribution loop, device 100 a enters an idlestate, in which it awaits further announcements, instructions, and/orrequests.

Device 100 b also receives the announcement from the carrier 110, whichtriggers an interaction in which the device 100 b can request missingportions from the carrier 110. In other embodiments, the device 100 binitiates the process of obtaining missing portions from the carrier 110without awaiting the announcement or other initial communication fromthe carrier 110. This interaction between device 100 b and the carrier110 allows the content provider to assure that every device has receivedthe entire content item. Such an additional interaction may be requiredin order for the content provider to comply with regulations thatrequire certain content to be distributed to every vehicle in aspecified set of vehicles (e.g., a fleet, all vehicles of a givenmake/model/year, all vehicles in a given geographic location, etc.).

In some embodiments, after a passage of time or occurrence of othercondition, the content provider takes action to assure that every devicehas received the content item. For example, after a certain number ofhours pass, the content provider initiates communication (via thecellular network) with each of the devices to provide any missingportions.

3. Automatic Rate Control

FIGS. 4A-4D illustrate automatic rate control according to an exampleembodiment. Some embodiments independently vary the transmission ratesemployed by each of the communication devices in a given network inorder to optimize or at least improve throughput, network connectivity,and/or range.

FIG. 4A illustrates a problem associated with the use of uniformtransmission rates. FIG. 4A depicts a collection of devices. Each deviceis represented as a dot (point) centered in a circle. The circlerepresents the transmission range of a given device. When a circle of afirst device encompasses a dot that represents a second device, thefirst device is capable of transmitting data to the second device.Similarly, when a circle of a first device does not encompass a dot thatrepresents a second device, the first device is not capable oftransmitting data to the second device.

FIG. 4A illustrates an example distribution of nodes in a dynamic mobilenetwork, such as a vehicle-based network described herein. As can beseen, the nodes in the illustrated network are not uniformlydistributed. Some nodes, such as devices 100 a-100 c, are located withina cluster of nodes. Each of the devices 100 a-100 c are capable oftransmitting data to at least one other device, as illustrated by thefact that the circles of 100 a-100 c each encompass at least one otherdot.

Other nodes, such as devices 100 d-100 f, are located in fringe regions.Devices 100 d-100 f are not capable of transmitting data to any otherdevices, and are thus effectively excluded from the illustrated network.Of course, it is possible to increase the transmission range of each ofthe devices, so that network connectivity and reach is improved. Rangecan be increased in different ways, such as by increasing transmissionpower. At a given power level, range can be increased by lowering thedata rate. There is an inverse relationship between data rate and range.For example, 54, 24, 12 Mbps transmissions may respectively have outdoorranges of 35, 100, and 200 meters. Given that regulations typicallylimit the maximum transmission power that can be used by wirelessradios, modifying data rate is in some contexts the preferred way tomodify transmission range.

In the example of FIG. 4A, simply decreasing the data rate of all radioswill cause the overall performance of the network to suffer, given theinverse relationship between transmission range and data rate (whenpower is held constant). In particular, if every device increasestransmission range (at a cost of lower data rate), the devices would bemore completely connected but at the cost of lower transmission ratesfor each of the devices. As will be discussed further below, thedescribed automatic rate control techniques address this problem byindependently and dynamically modifying the date rates employed by eachdevice.

FIGS. 4B-4D illustrate the problem and proposed solution in the contextof a small example network that includes only three devices 100 a-100 c,for purposes of exposition.

FIG. 4B illustrates the problem introduced with respect to FIG. 4A. InFIG. 4B, devices 100 a-100 c each employ a uniform data transmissionrate that is relatively high, but correspondingly short in range.Devices 100 a and 100 b are located within transmission range of oneanother, while device 100 c is out of range of devices 100 a and 100 b.

FIG. 4C illustrates a nave solution to the problem of FIG. 4B. In FIG.4C, devices 100 a-100 c each employ a uniform data transmission ratethat is relatively low (e.g., compared to that of FIG. 4B), butcorrespondingly long in range. Thus, each device is able to transmit toat least one other device. The increased transmission range results infull connectivity at the expense of lower transmission data rates.

FIG. 4D illustrates a preferred solution to the problem of FIG. 4B. InFIG. 4D, devices 100 a-100 c each employ a data transmission rate thatis tuned to provide high connectivity in addition to high data rateswhere possible. For example, the tightly clustered devices 100 a and 100b employ a high data rate (with a corresponding short range), while thefringe device 100 c employs a low data rate (with a corresponding longrange). In FIG. 4D, each device is able to transmit to at least oneother device, but at least some of the devices are able to transmit dataat rates higher than those employed in FIG. 4C, yielding an aggregateperformance increase.

FIG. 5 is a sequence diagram that illustrates an automatic rate controlprocess according to an example embodiment. The automatic rate controlprocess described with respect to FIG. 5 seeks to obtain configurationssimilar to the one shown with respect to FIG. 4D, where each deviceemploys a data rate that is adapted to dynamic geospatial layout of anetwork of devices. In general, upon the operation of the illustratedprocess, tightly clustered devices will transmit at high data rates andcorrespondingly short ranges, while fringe devices will transmit at lowdata rates and correspondingly long ranges.

In FIG. 5, three devices 100 a-100 c dynamically adjust data rates inorder to optimize or improve network performance and reachability. Inthis example, from spatial perspective, devices 100 a and 100 c arefringe nodes, while device 100 b is more centrally located.

The operations of the process of FIG. 5 typically take place in thecontext of an encompassing peer-to-peer distribution process, such asthat described with respect to FIG. 3. In an initial condition, thedevices 100 a-100 c transmit data in a sub-optimal manner, as describedwith respect to FIGS. 5A and 5B. Device 100 a can directly communicatewith device 100 b, but not device 100 c. Similarly, device 100 c candirectly communicate with device 100 b, but not device 100 c. Due tothis connectivity restriction, a portion transmitted by device 100 c todevice 100 a must first be transmitted to device 100 b, which thenfurther transmits it to destination device 100 a. While it is at leastpossible in this scenario for device 100 c to transmit data to device100 a, such communication likely results in a performance penalty due tothe additional required “hop” through device 100 b, in addition to theadditional burden placed on the resources of device 100 b itself.

In order to improve connectivity and performance, each device 100 a-100b adjusts its data rate according to the following logic. Each devicemonitors the current carrier or medium utilization level, here expressedas the fraction of time that the “air” (radio channel or frequency usedfor communication with other devices) is idle. If the carrier is lessthan 50% idle, the data rate is increased. This is a condition that willtypically be experienced by devices located in a cluster of devices,where many devices are competing for use of the carrier. By increasingthe data rate, the transmission range for the device will decrease andthe fraction of idle time will increase. In the scenario of FIG. 4A,this will have the effect of “shrinking” the circles (representingtransmission distance) corresponding to the devices in the centercluster. As a result, the clustered devices will be able to communicatewith one another at high data rates.

On the other hand, if the carrier is more than 50% idle, the data rateis decreased. This is a condition that will typically be experienced bydevices located on the fringes of the network or otherwise far removedfrom other devices. By decreasing the data rate, the transmission rangefor the device will increase and the fraction of idle time willdecrease. In the scenario of FIG. 4A, this will have the effect of“growing” the circles (representing transmission distance) correspondingto the isolated devices on the fringes. As a result, the fringe deviceswill be able to communicate with devices in the inner cluster and/orother fringe devices. Overall, by selectively modifying datatransmission rates at each device depending on conditions sensed by thedevice, network connectivity and aggregate performance are increased.

Note that the above-described process operates continuously, such thatchanging conditions will lead to device-level adjustments. In mobilenetworks, the spatial arrangement of the communicating devices typicallychanges over time. For example, in a vehicle based network, cars along asection of road become compressed around traffic lights or stop signs,while those same cars spread out along the open stretches of road. Insuch cases, each vehicle-based device will continuously monitor the idlelevel and make adjustments accordingly, thereby reacting dynamically tochanges in the physical arrangement of the vehicles.

The above-described techniques can be modified in other embodiments. Forexample, different thresholds can be employed. Thus, rather than using50% idle as the threshold for increasing/decreasing data rate, otherthresholds may be employed (e.g., 30%, 40%, etc.) Also, data rate may beincreased in various ways or rates, such as in a linear or non-linearmanner based on the difference between the detected actual idle leveland the threshold idle level. Device reactivity may also be dampened,such as by measuring an average idle level over a specified time period(e.g., 5, 10, or 30 seconds).

As noted, transmission range may also be modified by adjusting radiotransmission power. Some embodiments may increase transmission range byincreasing transmission power, possibly in combination with a decreasein data rate.

4. Example Processes

FIGS. 6A-6M are example flow diagrams of content distribution processesperformed by example embodiments.

FIG. 6A is a flow diagram of example logic in a first vehicle-basedcommunication device. The illustrated logic in this and the followingflow diagrams may be performed by, for example, the content distributionmodule 200 and/or other devices or systems, such as the content providercomputing system 60 described with respect to FIG. 7, below. Thisparticular process manages the peer-to-peer distribution of content asdescribed with respect to FIG. 3, above. More particularly, FIG. 6Aillustrates a process 6A00 that includes the following block(s).

Block 6A01 includes receiving, via a cellular network, a content itemfrom a content distributor. The process receives the content item fromthe content distributor via a cellular network, such as a GSM, UMTS, orLTE network. In some embodiments the process need only receive a portionof the content item prior to beginning to further distribute the contentitem to other devices. The content item may be code, data, personalmedia, or the like.

Block 6A02 includes transmitting, via a Wi-Fi network, a first portionof the content item to a second vehicle-based communication device,wherein the first portion is randomly selected by the first device. Thesecond network is typically a Wi-Fi network. In a vehicle-based contextthe second network may be a 802.11p network or similar designed forvehicle-based operation. The content item is broken up into portions,which may be of fixed or variable size. The transmitted portion isselected as random, as the process does not necessarily have anyknowledge of what portions have already been received by nearby devices.The transmission typically takes the form of a broadcast, so thatmultiple nearby devices may receive the benefit of the transmission of asingle portion. The first portion is transmitted as a “push”transmission, that is, it is transmitted not in response to any requestfor the portion received from other devices.

Block 6A03 includes receiving, via the Wi-Fi network, a request for asecond portion of the content item from the second device. The processis also configured to provide portions in an “on demand” manner tonearby devices. In this way, when a nearby device seeks to complete acontent item by obtaining a last few missing portions, the nearby devicecan broadcast a request for a specific portion.

Block 6A04 includes in response to the received request, transmit, viathe Wi-Fi network, the second portion of the content item to the seconddevice. Again, the transmission here may be in the form of a broadcastso that some other devices may also receive the requested portion.

FIG. 6B is a flow diagram of example logic illustrating an extension ofprocess 6A00 of FIG. 6A. More particularly, FIG. 6B illustrates aprocess 6B00 that includes the process 6A00, and which further includesthe following block(s).

Block 6B01 includes receiving from the content distributor anannouncement that identifies the content item, the announcement receivedvia the cellular network. These operations typically precede thetransmission of the content item itself, as described above. Theannouncement is a message that identifies the content item fordistribution, and possibly the source or other metadata related to thecontent item. The announcement may itself be cryptographically signed,so that its source can be authenticated.

Block 6B02 includes in response to the announcement, transmitting arequest via the cellular network to the content distributor for theidentified item. Having received the announcement, the process respondsto the content distributor with a request for the identified contentitem, if it has not already received it from another source, such assome other vehicle-based device.

Block 6B03 includes receiving from the content distributor proofsconfigured to authenticate the content item, the proofs received via thecellular network. The process receives a set of proofs, which includedata that can be used to verify the content (e.g., that the content hasnot been corrupted) and/or the source of the content (e.g., the identityof the content provider or some other party that is the author orprovider of the content). As discussed above, Merkle proofs may beemployed to provide at least some of this functionality.

Block 6B04 includes receiving, via the cellular network, the contentitem from the content distributor. Typically, after using the proofs toauthenticate the source of the content item, the process receives thecontent item via the first network. The content item may be broken upinto portions, such that receiving the content item includes receivingmultiple separate portions of the content item.

FIG. 6C is a flow diagram of example logic illustrating an extension ofprocess 6B00 of FIG. 6B. More particularly, FIG. 6C illustrates aprocess 6C00 that includes the process 6B00, and which further includesthe following block(s).

Block 6C01 includes authenticating the source and content of the contentitem based on the proofs received from the content distributor.Authenticating the source and content may include operations such asverifying a digital signature and/or message digest. The integrity ofthe content item may be checked incrementally (e.g., as portions arereceived) or once the entire content item is received.

FIG. 6D is a flow diagram of example logic illustrating an extension ofprocess 6B00 of FIG. 6B. More particularly, FIG. 6D illustrates aprocess 6D00 that includes the process 6B00, and which further includesthe following block(s).

Block 6D01 includes receiving from the second device a request for theannouncement, the request transmitted via the Wi-Fi network by thesecond device in response to receipt of the first portion of the contentitem. When the process randomly broadcasts a portion to the seconddevice, the second device may have no knowledge of the content itembeing distributed. If such is the case, the second device will respondwith a request for the announcement, so that the second device candetermine the identity, source, nature, and/or purpose of the contentitem.

Block 6D02 includes transmitting via the Wi-Fi network the announcementto the second device. The announcement may be accompanied by the proofsas well. Alternatively, the proofs may be transmitted in response to aspecific request therefor.

FIG. 6E is a flow diagram of example logic illustrating an extension ofprocess 6A00 of FIG. 6A. More particularly, FIG. 6E illustrates aprocess 6E00 that includes the process 6A00, and which further includesthe following block(s).

Block 6E01 includes transmitting, via the Wi-Fi network, randomlyselected portions of the content item to the second device. The processconcurrently performs two main operations during content itemdistribution. In this operation, the process repeatedly transmitsrandomly selected portions until some stopping condition is reached.

Block 6E02 includes responding to requests received from the seconddevice for specified portions of the content item by transmitting, viathe Wi-Fi network, the specified portions to the second device. In thisoperation, typically performed concurrently with the above, the processresponds to any requests for specific content portions, such as thosereceived from devices that are seeking missing portions that will serveto complete the entire content item. In some embodiments, a device thathas received more than some threshold (e.g., 90%) of the portions thatmake up a particular content item will begin to broadcast requests forthose missing portions. Responsive devices may employ a scheme thatprevents multiple devices from responding to the request, such aswaiting for a random time interval before responding, and then onlyresponding if no other device has begun transmitting the requestedportion. Alternatively or in addition, devices that are seeking missingportions can communicate with the content distributor (via the cellularnetwork) in order to obtain the missing portions.

FIG. 6F is a flow diagram of example logic illustrating an extension ofprocess 6A00 of FIG. 6A. More particularly, FIG. 6F illustrates aprocess 6F00 that includes the process 6A00, and which further includesthe following block(s).

Block 6F01 includes repeatedly transmitting, via the Wi-Fi network,randomly selected portions of the content item, wherein the transmissionis a broadcast transmission that reaches multiple other vehicle-basedcommunication devices that are part of the Wi-Fi network. As discussedabove, the transmission of content items via the Wi-Fi or other networkis typically in the nature of a broadcast, so that multiple otherdevices that are in the range of the transmission can benefit from asingle transmission.

FIG. 6G is a flow diagram of example logic for distributing content in avehicle-based wireless network. This process is performed by a contentdistributor that seeks to distribute a content item to devices in avehicle-based network. More particularly, FIG. 6G illustrates a process6G00 that includes the following block(s).

Block 6G01 includes transmitting, via a cellular network, anannouncement, proofs, and a content item to a first subset of devices inthe vehicle-based wireless network, wherein the announcement istransmitted by a content distributor and identifies a content item, andwherein the proofs are configured to authenticate the contentdistributor and the content item. The content distributor firsttransmits the announcement, proofs, and at least some of the contentitem to some of the devices in the network. This data is transmitted viathe cellular network, which is typically a cellular network, such as a3G/4G network.

Block 6G02 includes causing devices in the first subset of devices totransmit, via a Wi-Fi network, portions of the content item to devicesin a second subset of devices in the vehicle-based wireless network.Once a device in the network receives the announcement, correspondingproofs, and at least some of the content item, the device will begin toshare portions of the content item via the Wi-Fi network. The devices inthe second subset are those that have not received the announcement,proofs, or content item from the distributor. At this point, the contentdistributor waits to allow the content item (or at least portionsthereof) to be shared throughout the network.

Block 6G03 includes transmitting, via the cellular network, remainingportions to the devices in the second subset of devices, wherein eachremaining portion is one that has not been received by a device in thesecond subset of devices from any of the devices in the first subset ofdevices. After some time, the content distributor engages devices in thesecond subset, which never received the initial announcement or contentitem from the content distributor. The content distributor can therebyassure that the content item has been fully distributed by transmittingany missing portions to devices of the second subset.

FIG. 6H is a flow diagram of example logic illustrating an extension ofprocess 6G00 of FIG. 6G. More particularly, FIG. 6H illustrates aprocess 6H00 that includes the process 6G00, and which further includesthe following block(s).

Block 6H01 includes tracking distribution of the content item throughoutthe vehicle-based network. Tracking distribution of the content item caninclude sampling a randomly selected subset of devices to determine howmuch of the content item has been received by each device. By trackingdistribution, the content distributor can determine how much and howquickly the content item is being shared across the network.

Block 6H02 includes in response to the distribution of the content itemreaching a threshold level, transmitting the remaining portions to thedevices in the second subset. For example, once the content item is 70%distributed (e.g., each device has received an average of 70% of therelevant portions), the distributor interacts with the devices in thesecond subset to assure that every device in the network receives theentire content item.

FIG. 6I is a flow diagram of example logic illustrating an extension ofprocess 6G00 of FIG. 6G. More particularly, FIG. 6I illustrates aprocess 6I00 that includes the process 6G00, and which further includesthe following block(s).

Block 6I01 includes receiving, by a roadside communication device andvia the Wi-Fi network, a content portion from a first vehicle-basedcommunication device, wherein the roadside communication device islocated at a fixed position about a roadway traveled by a vehicle thatcarries the first device. Some embodiments include fixed positionroadside devices that are configured to forward content portions fromone vehicle to another. Some roadside devices may also have multiplecommunication interfaces, such that they can also communicate with thecontent distributor via a cellular network (or wireline network) toreceive content which is to be forwarded to vehicle-based devices in thenetwork.

Block 6I02 includes transmitting, by the roadside communication deviceand via the Wi-Fi network, the content portion to a second vehicle-basedcommunication device. In this example, the roadside device operates in asimilar manner to the vehicle-based devices, in that it receives contentportions broadcast by passing vehicles, and then forwards those portionsto other vehicles. As noted, the roadside device may also receivecontent directly from the content distributor, possibly via some othercommunication interface, such as wireline, cellular, or the like.

FIG. 6J is a flow diagram of example logic in a first vehicle-basedcommunication device for distributed storage of content items in avehicle-based wireless network. This process automatically adjusts thedata transmission rate of a device in the network in order to improvenetwork connectivity and overall performance, as discussed with respectto FIGS. 4A-4D and 5, above. More particularly, FIG. 6J illustrates aprocess 6J00 that includes the following block(s).

Block 6J01 includes determining a utilization level for a wirelesschannel used to communicate with other vehicle-based communicationdevices in the network. The channel is the frequency or frequency bandthat is used by the device to communicate with other devices. Bylistening on the channel, the process can determine the fraction of timethat the channel is busy or idle. In this example, utilization isequated with idleness, although it is possible to use business instead,with a corresponding reversal of the logic described below.

Block 6J02 includes when the utilization level is below a thresholdlevel, increasing transmission data rate of a first wireless transceiverof the first device. When utilization is measured as idle time, then theprocess will increase data rate when the channel is less than athreshold percentage idle (e.g., less than 50% idle). As noted, giventhe inverse relationship between data transmission rate and range, thiswill have the effect of shortening the transmission range.

Block 6J03 includes when the utilization level is above a thresholdlevel, decreasing the transmission data rate of the first wirelesstransceiver. For example, when the channel is more than 50% idle, theprocess will decrease the transmission data rate, thereby increasingrange.

Block 6J04 includes transmitting data to other vehicle-basedcommunication devices in the network. The established data rate will beuse for transmission. The above operations are typically repeatedlyperformed to dynamically adapt to changes in the network topology andutilization.

FIG. 6K is a flow diagram of example logic illustrating an extension ofprocess 6J00 of FIG. 6J. More particularly, FIG. 6K illustrates aprocess 6K00 that includes the process 6J00, wherein the determining autilization level for a wireless channel includes the followingblock(s).

Block 6K01 includes determining a percentage of time that the wirelesschannel is idle, measured over a specified time interval. Utilizationcan be determined by listening on the channel and measuring whatpercentage of time the channel is quiet over a time interval (e.g., 1,5, 10 seconds).

FIG. 6L is a flow diagram of example logic illustrating an extension ofprocess 6J00 of FIG. 6J. More particularly, FIG. 6L illustrates aprocess 6L00 that includes the process 6J00, and which further includesthe following block(s).

Block 6L01 includes receiving, via a second wireless transceiver of thefirst device, a content item from a content distributor. As discussedabove, typical devices have two communication interfaces, one forcellular communication (e.g., with the content distributor) and anotherfor local communication with other devices/vehicles. Here the devicereceives content via the cellular interface, such as is described withrespect to FIG. 3, above.

Block 6L02 includes transmitting, via the first wireless transceiverusing the transmission data rate, portions of the content item to othervehicle-based communication devices in the network. The device then usesthe established data rate to forward portions of the content item toother devices in the network via the Wi-Fi interface.

FIG. 6M is a flow diagram of example logic illustrating an extension ofprocess 6J00 of FIG. 6J. More particularly, FIG. 6M illustrates aprocess 6M00 that includes the process 6J00, and which further includesthe following block(s).

Block 6M01 includes automatically adjusting transmission data rate whenthe first device is in close proximity to other devices in the network,such that the first device transmits at a higher rate over a shorterdistance relative to other devices in the network that that are not inclose proximity to other devices. Proximity may be measured andexpressed in various ways. For example, proximity may be an averagedistance to other vehicles (possibly within some maximum range). Thosevehicles that are in close proximity to other vehicles will tend to bein a cluster, meaning that their channels will tend to be busy (notidle), which in turn will result in higher data rates (and shortedtransmit ranges) by operation of the described techniques. Similarly,those in low proximity (high average distance to other devices) willtend to experience higher idle levels on their channels, which in turnwill result in lower data rates (and longer transmit ranges). In theend, the described processes will cause clustered nodes to transmitquickly, while edge or fringe nodes to transmit far.

5. Example Computing System Implementation

FIG. 7 is a block diagram of an example computing system or device forimplementing and performing content distribution according to an exampleembodiment. In particular, FIG. 7 shows a computing system or device 100that executes a content distribution module 200 that implements at leastsome of the techniques described herein. The device 100 may be, in thecase of a vehicle-based network, installed in a car or other vehicle. Inother contexts, the device 100 may be a mobile device, such as a tabletor smart phone.

Note that one or more general purpose or special purpose computingsystems/devices may be used to implement and/or execute the module 200.However, just because it is possible to implement the manager on ageneral purpose computing system does not mean that the techniquesthemselves or the operations (taken alone or in combination) required toimplement the techniques are conventional or well known. In addition,the computing system 100 may comprise one or more distinct computingsystems/devices and may span distributed locations. Furthermore, eachblock shown may represent one or more such blocks as appropriate to aspecific embodiment or may be combined with other blocks. Also, themodule 200 may be implemented in software, hardware, firmware, or insome combination to achieve the capabilities described herein.

In the embodiment shown, computing system 100 comprises a computermemory (“memory”) 11, a display 12, one or more Central Processing Units(“CPU”) 13, Input/Output devices 14 (e.g., keyboard, mouse, CRT or LCDdisplay, and the like), other computer-readable media 15, and networkconnections 16 a and 16 b. The module 200 is shown residing in memory11. In other embodiments, some portion of the contents, some or all ofthe components of the module 200 may be stored on and/or transmittedover the other computer-readable media 15. The module 200 preferablyexecutes on one or more CPUs 13 and performs the techniques describedherein. Other code or programs 30 (e.g., an administrative interface, aWeb server, and the like) and potentially other data repositories, suchas data repository 20, also reside in the memory 11, and preferablyexecute on one or more CPUs 13. Of note, one or more of the componentsin FIG. 7 may not be present in any specific implementation. Forexample, some embodiments may not provide other computer readable media15 or a display 12.

The module 200 interacts using network connection 16 a via a Wi-Finetwork 99 a with other devices 100′ and 100″. The module 200 alsointeracts using network connection 16 b via a carrier network 99 b witha content provider computing system 60. The other devices 100′ and 100″are constituted similarly to device 100. One or more of devices 100′ and100″ may be located at fixed positions, such as at the side of a roadway(e.g., mounted on a utility pole or traffic signal).

The module 200 is shown executing in the memory 11 of the device 100.Also included in the memory 11 are a user interface manager 41 and anapplication program interface (“API”) 42. The user interface manager 41and the API 42 are drawn in dashed lines to indicate that in otherembodiments, functions performed by one or more of these components maybe performed externally to the module 200.

The UI manager 41 provides a view and a controller that facilitate userinteraction with the module 200 and its various components. For example,the UI manager 41 may provide interactive access to the module 200, suchthat users or administrators can interact with the module 200, such asby modifying configuration settings, viewing logs, or the like. In someembodiments, access to the functionality of the UI manager 41 may beprovided via a Web server, possibly executing as one of the otherprograms 30. In such embodiments, a user operating a Web browserexecuting the network management system 55 can interact with the module200 via the UI manager 41.

The API 42 provides programmatic access to one or more functions of themodule 200. For example, the API 42 may provide a programmatic interfaceto one or more functions of the module 200 that may be invoked by one ofthe other programs 30 or some other module. In this manner, the API 42facilitates the development of third-party software, such as userinterfaces, plug-ins, adapters (e.g., for integrating functions of themodule 200 into Web applications), and the like.

In addition, the API 42 may be in at least some embodiments invoked orotherwise accessed via remote entities, such as code executing on one ofthe network devices 100′ and 100″ and/or the content provider computingsystem 60, to access various functions of the module 200. For example,the system 60 may transmit an announcement, a proof, a content portion,or other data item via the API 42. The system 60 may also interrogatethe module 200 for state information, including the how many contentportions have been received, log messages, or the like.

In an example embodiment, components/modules of the module 200 areimplemented using software programming techniques. For example, themodule 200 may be implemented as a “native” executable running on theCPU 13, along with one or more static or dynamic libraries. In otherembodiments, the module 200 may be implemented as instructions processedby a virtual machine that executes as one of the other programs 30.

In general, a range of programming languages may be employed forimplementing such example embodiments, including representativeimplementations of various programming language paradigms, including butnot limited to, object-oriented (e.g., Java, C++, C#, Visual Basic.NET,Smalltalk, and the like), functional (e.g., ML, Lisp, Scheme, and thelike), procedural (e.g., C, Pascal, Ada, Modula, and the like),scripting (e.g., Perl, Ruby, Python, JavaScript, VBScript, and thelike), and declarative (e.g., SQL, Prolog, and the like).

The various components may be implemented using more monolithicprogramming techniques, for example, as an executable running on asingle CPU computer system, or alternatively decomposed using a varietyof structuring techniques, including but not limited to,multiprogramming, multithreading, client-server, or peer-to-peer,running on one or more computer systems each having one or more CPUs.Some embodiments may execute concurrently and asynchronously, andcommunicate using message passing, remote procedure call, or otherdistributed computing paradigms. Equivalent synchronous embodiments arealso supported. Also, other functions could be implemented and/orperformed by each component/module, and in different orders, and bydifferent components/modules, yet still achieve the described functions.

In addition, programming interfaces to the data stored as part of themodule 200, such as in the data store 20, can be available bylanguage-specific APIs; libraries for accessing files, databases, orother data repositories; through representational languages such as XML;or through Web servers, FTP servers, or other types of servers providingaccess to stored data. The data store 20 may be implemented as one ormore database systems, file systems, or any other technique for storingsuch information, or any combination of the above, includingimplementations using distributed computing techniques.

Different configurations and locations of programs and data arecontemplated for use with techniques of described herein. A variety ofdistributed computing techniques are appropriate for implementing thecomponents of the illustrated embodiments in a distributed mannerincluding but not limited to TCP/IP sockets, RPC, RMI, HTTP, WebServices (XML-RPC, JAX-RPC, SOAP, and the like). Other variations arepossible. Also, other functionality could be provided by eachcomponent/module, or existing functionality could be distributed amongstthe components/modules in different ways, yet still achieve thefunctions described herein.

Furthermore, in some embodiments, some or all of the components of themodule 200 may be implemented or provided in other manners, such as atleast partially in firmware and/or hardware, including, but not limitedto one or more application-specific integrated circuits (“ASICs”),standard integrated circuits, controllers executing appropriateinstructions, and including microcontrollers and/or embeddedcontrollers, field-programmable gate arrays (“FPGAs”), complexprogrammable logic devices (“CPLDs”), and the like. Some or all of thesystem components and/or data structures may also be stored as contents(e.g., as executable or other machine-readable software instructions orstructured data) on a computer-readable medium (e.g., as a hard disk; amemory; a computer network or cellular wireless network or other datatransmission medium; or a portable media article to be read by anappropriate drive or via an appropriate connection, such as a DVD orflash memory device) so as to enable or configure the computer-readablemedium and/or one or more associated computing systems or devices toexecute or otherwise use or provide the contents to perform at leastsome of the described techniques. Some or all of the components and/ordata structures may be stored on tangible, non-transitory storagemediums. Some or all of the system components and data structures mayalso be stored as data signals (e.g., by being encoded as part of acarrier wave or included as part of an analog or digital propagatedsignal) on a variety of computer-readable transmission mediums, whichare then transmitted, including across wireless-based andwired/cable-based mediums, and may take a variety of forms (e.g., aspart of a single or multiplexed analog signal, or as multiple discretedigital packets or frames). Such computer program products may also takeother forms in other embodiments. Accordingly, embodiments of thisdisclosure may be practiced with other computer system configurations.

While embodiments of the invention have been illustrated and described,as noted above, many changes can be made without departing from thespirit and scope of the invention. Accordingly, the scope of theinvention is not limited by the above disclosure.

1. A system for distributing content in a vehicle-based wirelessnetwork, the system comprising: a first vehicle-based communicationdevice; a second vehicle-based communication device; wherein the firstdevice is configured to: receive, via a cellular network, a content itemfrom a content distributor; transmit, via a Wi-Fi network, a firstportion of the content item to the second vehicle-based communicationdevice, wherein the first portion is randomly selected by the firstdevice; receive, via the Wi-Fi network, a request for a second portionof the content item from the second device; and in response to thereceived request, transmit, via the Wi-Fi network, the second portion ofthe content item to the second device; and wherein the second device isconfigured to: request, via the cellular network, a third portion fromthe content distributor; and receive, via the cellular network, thethird portion.
 2. The system of claim 1, further comprising: a contentdistributor that is configured to: transmit, via the cellular network,an announcement to the first device, the announcement identifying thecontent item; in response to the announcement, receive from the firstdevice a request for the identified content item; transmit, via thecellular network, proofs to the first device, the proofs configured toauthenticate the content item; and transmit, via the cellular network,the content item to the first device.
 3. The system of claim 2, whereinthe first device is further configured to: authenticate the source andcontents of the content item based on the proofs received from thecontent distributor.
 4. The system of claim 2, wherein the second deviceis further configured to: in response to receipt of the first portion ofthe content item via the Wi-Fi network from the first device, transmitvia the Wi-Fi network a request for the announcement to the firstdevice; and receive the announcement from the first device via the Wi-Finetwork.
 5. The system of claim 2, wherein the content distributor isfurther configured to: transmit, via the cellular network, theannouncement to the second device; and transmit, via the cellularnetwork, portions of the content items to the second device, wherein thetransmitted portions are portions that the second device has notreceived via the Wi-Fi network.
 6. The system of claim 2, wherein thecontent distributor is further configured to: transmit, via the cellularnetwork, an announcement, proofs, and a content item to a first subsetof devices in the vehicle-based wireless network, wherein theannouncement identifies a content item, and wherein the proofs areconfigured to authenticate a source of the content item and the contentitem itself; cause devices in the first subset of devices to transmit,via the Wi-Fi network, portions of the content item to devices in asecond subset of devices in the vehicle-based wireless network; andtransmit, via the cellular network, remaining portions to the devices inthe second subset of devices, wherein each remaining portion is one thathas not been received by a device in the second subset of devices fromany of the devices in the first subset of devices, thereby assuring thateach of the devices in the second subset receives the entire contentitem.
 7. The system of claim 1, wherein the first device is furtherconfigured to: transmit, via the Wi-Fi network, randomly selectedportions of the content item to the second device; and respond torequests received from the second device for specified portions of thecontent item by transmitting, via the Wi-Fi network, the specifiedportions to the second device.
 8. The system of claim 1, wherein thefirst device is further configured to: repeatedly transmit, via theWi-Fi network, randomly selected portions of the content item, whereinthe transmission is a broadcast transmission that reaches multiple othervehicle-based communication devices that are part of the Wi-Fi network.9. The system of claim 1, further comprising: at least one roadsidecommunication device that is located in a fixed position about a roadwayand that is configured to: receive, via the Wi-Fi network, a contentportion from the first device; and transmit, via the cellular network,the content portion to the second device.
 10. The system of claim 1,wherein the Wi-Fi network is an 802.11p network.
 11. The system of claim1, wherein the content item is a software update for a computing systemin a vehicle.
 12. A method in a first vehicle-based communicationdevice, the method comprising: receiving, via a cellular network, acontent item from a content distributor; transmitting, via a Wi-Finetwork, a first portion of the content item to a second vehicle-basedcommunication device, wherein the first portion is randomly selected bythe first device; receiving, via the Wi-Fi network, a request for asecond portion of the content item from the second device; and inresponse to the received request, transmit, via the Wi-Fi network, thesecond portion of the content item to the second device.
 13. The methodof claim 12, further comprising: receiving from the content distributoran announcement that identifies the content item, the announcementreceived via the cellular network; in response to the announcement,transmitting a request via the cellular network to the contentdistributor for the identified item; receiving from the contentdistributor proofs configured to authenticate the content item, theproofs received via the cellular network; and receiving, via thecellular network, the content item from the content distributor.
 14. Themethod of claim 13, further comprising: authenticating the source andcontent of the content item based on the proofs received from thecontent distributor.
 15. The method of claim 13, further comprising:receiving from the second device a request for the announcement, therequest transmitted via the Wi-Fi network by the second device inresponse to receipt of the first portion of the content item; andtransmitting via the Wi-Fi network the announcement to the seconddevice.
 16. The method of claim 12, further comprising: transmitting,via the Wi-Fi network, randomly selected portions of the content item tothe second device; and responding to requests received from the seconddevice for specified portions of the content item by transmitting, viathe Wi-Fi network, the specified portions to the second device.
 17. Themethod of claim 16, further comprising: transmitting portions of thecontent item until all portions of the content item have beentransmitted to the second device, the transmitted portions selectedrandomly or based on requests received from the first device.
 18. Themethod of claim 12, further comprising: repeatedly transmitting, via theWi-Fi network, randomly selected portions of the content item, whereinthe transmission is a broadcast transmission that reaches multiple othervehicle-based communication devices that are part of the Wi-Fi network.19. The method of claim 12, wherein the cellular network is a 3G/4Gnetwork.
 20. A method for distributing content in a vehicle-basedwireless network, the method comprising: transmitting, via a cellularnetwork, an announcement, proofs, and a content item to a first subsetof devices in the vehicle-based wireless network, wherein theannouncement is transmitted by a content distributor and identifies acontent item, and wherein the proofs are configured to authenticate thecontent distributor and the content item; causing devices in the firstsubset of devices to transmit, via a Wi-Fi network, portions of thecontent item to devices in a second subset of devices in thevehicle-based wireless network; and transmitting, via the cellularnetwork, remaining portions to the devices in the second subset ofdevices, wherein each remaining portion is one that has not beenreceived by a device in the second subset of devices from any of thedevices in the first subset of devices.
 21. The method of claim 20,further comprising: tracking distribution of the content item throughoutthe vehicle-based network; and in response to the distribution of thecontent item reaching a threshold level, transmitting the remainingportions to the devices in the second subset.
 22. The method of claim20, further comprising: receiving, by a roadside communication deviceand via the Wi-Fi network, a content portion from a first vehicle-basedcommunication device, wherein the roadside communication device islocated at a fixed position about a roadway traveled by a vehicle thatcarries the first device; and transmitting, by the roadsidecommunication device and via the Wi-Fi network, the content portion to asecond vehicle-based communication device.